Conventionally, a known angular velocity detection device utilizes a capacity change due to a displacement of an oscillating body (refer to, for example, Patent Document 1). The angular velocity detection device has drive means for oscillating the oscillating body, and displacement detecting means for detecting displacements of the oscillating body in a plurality of directions. Such a displacement detecting means is configured (hereinafter referred to as “a single-amp system”) such that carrier signals of plural frequencies are applied to detection electrodes to detect a plurality of capacity changes, and charge signals are fetched out from a common terminal to perform capacity detection and detected based on the respective carrier signals to thereby detect respective displacement signals. Another displacement detecting means is configured (hereinafter referred to as “a multi-amp system”) such that a single carrier signal is applied to a common terminal, charge signals are fetched out from a plurality of detection electrodes and capacity-detected using independent circuits, and they are detected based on the carrier signal to thereby detect respective displacement signals.
A comparison is made between the single-amp system and the multi-amp system. In the single-amp system, the common terminal of the oscillating body is directly coupled to a capacity detection circuit. For this reason, when a higher harmonic is contained in a drive signal, the higher harmonic is inputted directly to a capacity detection unit via a drive electrode. The drive signal generally uses a large amplitude to obtain a sufficient oscillation amplitude, and the scale (capacity) of the drive electrode is also large. Therefore, the input to the capacity detection becomes a very large amplitude, and not only large detection error occurs, but also there is a saturation of the capacity detection unit due to an excessive input in many cases. For this reason, the drive signal is required to use a waveform (e.g., sine wave) in which higher harmonic is sufficiently suppressed, and the need for a large-scale low-pass filter (LPF) at the generation of a signal, and the like arise, thus resulting in an increase in cost.
In contrast, the multi-amp system does not undergo the effect of a drive signal since the common terminal of the oscillating body is driven by a carrier generation unit and it is low in impedance. Accordingly, input based on the drive signal to the capacity detection unit via the common terminal does not take place. For this reason, a waveform (e.g., rectangular wave) containing a large number of higher harmonics multiplied by odd numbers can be used for the drive signal, with the waveform (e.g., rectangular wave) being easy to generate, thereby making it possible to achieve a reduction in cost. Since the rectangular wave may have a small voltage amplitude for generating as much electrostatic force as each sine wave of the same amplitude, there is a merit of reducing power supply voltage.